The present invention relates to base stands for use in supporting fluid containers having generally hemispherical bottoms in an upright position and particularly to plastic base stands manufactured from recycled organic plastic material.
In recent years, plastic bottles have largely replaced glass bottles as the container of choice for holding pressurized fluids such as carbonated beverages. Typically, these plastic bottles are molded from polyethylene terephthalate (PET) material. However, due to the expense of the PET material, it is desirable to make the bottle as a whole, and particularly the side wall and bottom of the bottles using the least material possible consistent with the strength requirements for the bottle.
It is known that a hemispherical bottom can be employed to minimize the material employed. Unfortunately, a hemispherical bottom makes the bottle inherently unstable and requires a supporting structure to hold the bottle in the upright position. This is generally achieved by combining a base stand with the bottle. One method for adding a base stand is to integrate legs into the hemispherical bottom structure during the molding process as shown for example in U.S. Pat. No. 3,759,410. Unfortunately, extra material must be used in the molding process to ensure adequate material to form the legs which will retain their shape under the internal pressure of a carbonated liquid, adding as much as 10% additional material to the bottle and thereby increasing manufacturing costs. Food purity regulations require this additional material be virgin rather than recycled material since the integral legs are in direct contact with the contents of the container, Moreover, the formation of legs in the bottom of a bottle require more complex blow mold configurations which add to the complexity of the formation process, adding further cost.
Alternatively, base stands have been manufactured separately and joined to the bottle after the bottle has been formed. See, for example, U.S. Pat. Nos. 3,726,429; 4,138,026; 4,438,856; and 4,463,860. Currently, such base stands are typically injection molded from a virgin or recycled polyester resin to ensure recyclability of the container as a whole. Due to the flow characteristics of the polyester resin, the injection molding requires a certain minimum thickness in the molding cavity, typically in the order of about 0.006 inch. This minimum thickness permits the plastic to flow into, and fill, the cavity without blockage. Thus, injected molded base stands have a minimum wall thickness, dictated by the forming process rather than the physical limitations of the material used, which is excessive and thus stronger than necessary to perform its intended function. This excessive minimum wall thickness directly translates into excess material and therefore excess cost in the formation of the final product. A base stand that can be manufactured by a process that avoids the limitations of the injection molding process, using inexpensive, recycled materials to produce a thin-wall base stand would greatly reduce the manufacturing costs and would be welcome by bottle manufacturers. While some attempts have been made to vacuum form such base stands from thin sheet material, the process has not met with success.